US 7579218 B2
An LED display assembly, comprising a grid of electrical conductors; light emitting diodes in association with the grid and in electrical communication with the conductors that provide power for LED operation, the grid operable to receive heat from the diodes during diode operation, and the array configured for passing coolant fluid for transfer of heat to the fluid. LED packages adjustable relative to a mounting grid, are also provided.
1. The method that includes:
a) providing multiple LEDs positioned in a display array, and
b) selectively electrically energizing the LEDs in the array to adjust the display,
c) cooling the display array,
d) said cooling including passing a coolant fluid through a heat conductive first woven mesh associated with the array, and defining a mesh plane, all of the coolant flowing only generally parallel to said plane as it flows through the mesh,
e) and providing means for confining all of the coolant fluid to flow in and parallel to said plane of the mesh.
2. The method of
3. The method of
4. The method of
5. The method of
This application is a divisional application of Ser. No. 10/722,672, filed Nov. 28, 2003 now U.S. Pat. No. 7,144,748, which is a continuation-in-part of Ser. No. 10/625,185, filed Jul. 23, 2003 now U.S. Pat. No. 7,105,858.
The methods described and claimed herein relate generally to provision of electronic-optical packages, and more particularly to provision of grids or arrays of such packages supported in such manner as to facilitate their installation and use as in closely assembled or packed configurations.
Large-scale LED displays are typified by the use of T 1 ¾ (5 mm) packaged LEDs soldered to rigid printed circuit boards. Such circuit board/modules typically contain a large number of LEDs and must be replaced to correct for the failure of even a single LED. In addition to cost, weight and volume issues or problems, these displays are limited in resolution as a result of the LED package size (typically 0.2 inches in diameter), or about 300 times the plan form area of a bare LED (8000 times the volume), and they are limited in brightness by the small number of LEDs that can be placed in a given area, and also by the thermal resistance of the package and module design. The resolution limit is a function of spacing that is further restricted by package (LED) size. The brightness limit is a function of the number of LEDs per unit area and their individual light output, which is further dependent on the thermal resistance between the LED junction and the local environment. Also, existing LED signage and displays have limited ability to tailor the radiation emission pattern to the needs of the target/audience and thereby increase efficiency. Increased efficiency allows for reduced system and operating cost and/or more radiation delivered to the target.
There is need for improvements in the provision and operation of LED display assemblies that overcome problems of heating and inability to adequately transfer or dispose of heat generated by LED operation; problems of inadequate LED support on substrates or circuit boards; problems resulting from lack of flexibility of the LED support means; difficulties in manufacturing close packed LED displays; and other problems and difficulties as will appear.
It is a major object of the methods disclosed herein to provide ways for overcoming the above identified problems. Basically, the improved method includes:
a) forming an array, or grid of electrical conductors,
b) providing light emitting diodes located in association with the array and in electrical communication with the conductors that provide power for LED operation,
c) the array operable or operated to receive heat from the diodes during diode operation, and the array or grid configured for passing coolant fluid for transfer of heat to the fluid.
As will appear, the electrical conductors typically and advantageously may be provided in the form of insulated metallic wires which may be interwoven or configured to act as electrical and thermal conductors, and that also may serve as structural supports for arrays of LEDs. The LEDs may be selectively removed or replaced on such supports.
Another aspect of the improved method includes provision of an LED supporting means, such as a grid characterized by ease of conformance to selected shape, curvature, or complex configuration after the LED array is attached to the grid, the grid having flexibility to enable such compliance to desired shaping.
Another object is to effect and/or guide flow of coolant fluid through or along a shape compliant screen incorporating such LEDs. In this regard, the screen is amenable to fitting to
Yet another aspect of the invention is to provide a first protective sheet facing the diodes to pass light emitted by the diode array; and to provide a second sheet at the opposite side of the screen and diodes, the first and second sheets forming an enclosure within which coolant fluid is flowable. The screen itself may be dark or darkened to increase viewing contrast with the LED array, during its operation.
A further feature is provision of the electrical conductors to include primary conductors extending generally in one direction, and secondary conductors extending generally in another direction, the LEDs mounted on the primary conductors, and having terminals extending to the secondary conductors for electrical association thereto. In this regard, secondary conductors are typically provided to have one of the following:
Yet another feature is provision of a screen display incorporating diodes or diode devices, wherein each diode is provided to include a light emitter or emitters, a transparent container having a window area, the emitter supported within the container, and a reflector within the container to reflect emitted light toward said window. As will appear, an electrical lead or leads may be provided to extend with helical configuration within the container, such as a glass tube, to the emitter or emitters. The lead or leads may be formed to have flattened, or generally rectangular cross sections for stable support of the emitter or emitters.
The improved may include provision of a metallic base carrying the container, and through which said lead or leads extend. The base typically is formed to have an edge portion defining a recess for reception of a support for the diode, allowing diode rotation about the support. Multiple of the diodes may be supported by a conductor or conductors in a screen, and to have their windows oriented to face in the same or selected directions. The diodes may be rotated, or be rotatable, about axes defined by their supporting conductors.
Additional features include provision of certain power providing conductors that comprise first, second, and third pairs of wires to transmit electrical energization to red, green and blue LED pixels, respectively; provision of LED primary, secondary and tertiary wires electrically connected to the red, green and blue pixels, respectively, said primary wires clamp connected to said first pair of wires, said secondary wires clamp connected to said second pair of wires, and said tertiary wires clamp connected to said third pair of wires; provision for clamped nesting of such primary, secondary and tertiary wires; provision of certain conductors that extend at an acute angle or angles relative to others of said conductors; provision of protector means such as a plate or plate, or a screen or screens at the front or rear of the grid, and with air passing openings, as will appear.
The method as disclosed also includes:
a) providing multiple LEDs in a display array, and
b) selectively electrically energizing the LEDs in the array to adjust the display,
c) cooling the display array.
A further aspect of the includes selectively adjusting the positioning of the LEDs in the array to controllably vary the overall display.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:
Light emitting diodes are located or mounted in an array on various conductors, as shown on crests of conductor 12, and in such manner that each diode is in electrical communication with two conductors, establishing a circuit path from a conductor 11 to a conductor 12, via the diode internal circuit. See conductor energization controls 20 and 21 for two representation diodes 22 and 23, with circuit paths (for diode 22) at 24, 11 a, 22, 25, junction 26, 12 a, 12 b and 27; and circuit paths (for diode 23) at 28, 11 b, 23, 29, junction 30, 12 a, 12 b, and 29. Controls 20 and 29 are interconnected so that diodes 22 and 23 can be selectively energized in timed relation. Diode 22 is mounted on the top side or crest of conductor 11 a, and diode 23 is mounted on the top side of conductor 11 b. Other diodes as shown are similarly mounted and selectively controlled by controls indicated in bank 31, controls 20 and 21 considered as part of that bank. Electrical connections to metallic wires in the conductors are made by removal of or penetration through conductor insulation. Wires 25 and 29 extend in the Y-direction, and may be insulated. Junctions as at 26 and 30 are provided on all crests of secondary conductors 12, and all LEDs are mounted on conductors 11, and protectively between sequential crests of conductors 12.
The electrical conductors may comprise insulated metal wires that act as electrical and thermal conductors and that also serve as structural load conductors, for arrays of such diodes. See for example
It will be understood that the screen as shown facilitates its bending or warping, particularly about an axis or axes parallel to the X-direction extents of conductors 11 to conform the screen to desired shape or shapes. This may alter the perceived LED illumination emanating from different portions of the screen, as may be desired.
Referring now to
An electrical lead or leads indicated at 156 extends with helical configuration into the tube and within the tube, to the emitter or emitters, that configuration providing support. The lead or leads preferably has or have a flattened or generally rectangular configuration seen in
The base 157 defines a through opening 163 passing the lead or leads; the base also defines an end recess 164 filled with potting compound 165 as for example epoxy resin. The lead or leads pass through that compound. The base also has an edge portion defining an annular recess 168, for reception of a package support or support portion 169, as for example a portion of the conductor 11 a as seen in
Numerals 313-315 designate three insulated copper wires from the three pixels, respectively, nested between the referenced wire pairs. A small amount of insulation is removed at wire regions to establish electrical connection between 313 and 306 and 307; between 314 and 308 and 309; and between 315 and 310 and 311. A stainless steel retainer 316 extends about the wire assembly, and holds the wires in compression at the central regions, for example as seen at 317, 318, and 319 in
Screens may be used in place of circuit boards and conductors on or as film circuitry. Screens can provide power and signal conduits as at 300 or 302 in
A preferred form of the invention appears in
As disclosed herein large-screen modular displays and signs are enabled, along with various curvatures and complex geometric forms. Also, large scale video displays, and projection displays as for billboards are made possible. Low volume, low mass, low cost, high brightness, high resolution and high efficiency are enabled. Double sided displays can be provided. LEDs can be placed on opposite sides of the screen, and the screen can serve as a pattern for LED placement.
LED bases can be placed on a transparent substrate, or the screen can be provided as a polymer film or sheet.
Screen and superstrate may collectively provide mechanical, structural strength. Superstrate may be thin or layered to allow second or third flexure modes. Superstrates may be thin to reduce sideways transmission of radiation from LEDs. Some LED sideways light transmission can be provided for integrating between pixels.
Provision is made for use of means to use conductive/red LEDs. Screen elements can be connected to side faces of LEDs via conductive adhesives, solder, amalgams, indium, stabilite22, and conductive grease. A metallic superstrate can be used.
Red LEDs can be provided with two conductors on same side (UEC red on sapphire) Superstrates may have high refractive indices to increase usable radiation (polycarbonate 1.59)
Superstrates may have transparent adhesive layer, thermoplastic, thermoset, pressure sensitive features.
The screen can be deformed after weaving, during manufacture, or deform screen before and/or during weaving. Screen warp and woof wires of different metals can be used to reduce the possibility of electrical shorting.
Another modification comprises an array of light emitting diodes periodically placed on the weft wires of a woven aluminum and/or copper screen (wire cloth) with the weft wires acting as one conductor, and the warp wires acting as the opposite conductor. The wires may be electrically isolated at their crossing points by such means as anodic coatings and/or by the addition of inorganic or organic over-coatings. The LEDs can be activated by pulsed and/or continuous current and may be addressed as a whole or in groups or individually as in an active video display by control of conductor energization. Woven wire screen provides a very low cost substrate.
Additional benefits include efficient heat transport, low mass, low volume, reel to reel manufacturing with screen travel between reels and roll-up on a reel with LEDs placed in position. This allows freedom of display shape, transportable in a roll, ability to be held in tension, in a wide range of materials and sizes.
A video display may include an X-Y grid of light emitting diodes placed on an aluminum woven screen suspended or placed between a transparent polycarbonate sheet and another enclosing sheet on the opposite side. An aluminum sheet with gaps between the screen and the enclosing sheet become sufficient to allow forced air to enter and flow upward between the polycarbonate sheet and the screen, through the screen and exiting at the top rearmost part of the screen.
Conductor wires act as structural conductors, electrical conductors, and thermal conductors, and may also be provided with a black region made especially effective because of “cavity effect”. Wires may vary in size, materials, coatings etc. with axis, e.g. stainless steel wire may be used in tension in one axis direction and copper or aluminum wire of smaller diameter may be used in opposite axis direction (i.e. X-Y axes).
Manufacture may include placement of a screen on PTFE coated needle/cone array/drum to allow coating of die/wire bond/adhesive attach/screen without clogging holes; then forcing fluid through the screen to prevent clogging. Screens can be spaced apart by use of beads or spheres.
Electrostatic or electromagnetic powering of LEDs is possible, and particularly pulsed operation, as with LED video displays. High applied voltage allows smaller conductor cross sections.
LEDs with junction faces on metal, or with good junction heat transfer/thermal capacitance, can withstand very high voltage spikes.
Patterned superstrate and/or substrate may act as one conductor and screen or substrate as another conductor.
Anisotropic screens may be provided with wires along one axis of a different material than wires extending along another axis (thickness, form, alloy. Tensile strength and flexibility may be more important in one axis e.g. opposite roll axis or row axis; dissimilar metals are more apt to form dielectric regions at points of contact and this may be encouraged via processing and/or choice of material properties and coatings; a current flow in one LED row may be several times greater than current flow in another LED row.
Advantages and benefits of the
SPATIAL TUNING: Benefits accruing from the ability to aim the radiation from the emitters to the target include a reduction in emitter cost and/or electrical system cost and/or operating cost and/or increased radiation delivered to the target. The herein described pixel package can be rotated as for example 360 degrees around it's axis and 360 degrees around an axis perpendicular to its' axis, and as a consequence has complete freedom of movement in both elevation and azimuth.
HORIZONTAL AXIS OPTICS: The target audience for signage and billboards typically moves horizontally as in vehicles. Horizontal axis optics provide for optimum control as the horizontal angular aperture is typically much greater than the vertical angular aperture.
ANGULAR APERTURE CONTROL: Minimizing the radiation beyond the angular extent needed for the task is an important element in minimizing cost. Maximizing the aperture to emitter size ratio allows a minimization of the angular extent of the output radiation. The herein described pixel design allows for a minimization of the output radiation by minimizing the emitter array size via close emitter spacing and a narrow gauge substrate and by maximizing the aperture size for a given pixel spacing.
BIFACIAL DISPLAY: Bifacial displays are possible with a single array of bifacial pixels or via a forward and rearward spaced pixel arrays, which may provide or allow differing energizing content to the displays. The pixel package allows mounting in front of or in back of the display “plane”. This allows one face to use pixel packages mounted on the front of the vertical wires and facing forward, and the opposite face to use pixel packages mounted on the opposite side of the wires and facing rearward. The packages may be displaced vertically to allow clearance.
TRANSPARENT DISPLAY: Displays can be made with a wide range of transparency to suit a variety of end uses.
OPTICAL EFFICIENCY: The pixel design allows for use of a linear emitter array coupled with a visible mirror film parabolic trough, to control radiation in the vertical axis. Horizontal axis radiation may be controlled by end reflectors of similar material and these may be curved to aid in the control of the angular extent of the radiation in the horizontal axis. This design minimizes the average number of reflections and provides for high efficiency for each reflection. The pixel optical system may be contained within a cylindrical glass envelope for environmental protection. Additional benefits of such an envelope include:
1) functioning as a circular compressive element to constrain the elastically deformed 3M VMF and thereby cause it to form a parabolic curve; (The film is typically specularly reflecting film such as 3M visible mirror film. The reflecting film may be paired with/attached to additional film/s to provide the desired mechanical and other properties. The film/s may also be adhered to the container walls and/or constrained by lands/ridges/bumps along the container walls.)
2) functioning as a container for a wide range of liquids, gels, solids, and/or smaller containers;
3) functioning as a refractive optical element.
CONTRAST RATIO: Increasing the contrast ratio allows an improvement in visibility and/or a reduction in radiative power for a given visibility. The herein described configuration allows high contrast ratio viewing by:
1) Minimizing the angular extent of the output radiation and increasing the aperture area of the output radiation reduces the probability of sunlight or other extraneous radiation being reflected from the “display” to the target/viewer,
2) Optical porosity (low solidity), which allows a portion of the radiation that would impinge on and possibly be reflected into the target on a high solidity display pass through and be absorbed on a subsidiary surface/s,
3) Insuring all surfaces within the targets field of view have very low reflectivity by means such as coating and texturing.
DETECTOR/DETECTOR ARRAY: The described pixel may also operate as detectors, alone or in conjunction with emitters.
The lifetime and efficiency of semiconductor devices (LEDs) degrades strongly with increasing temperature. Provision is made for reducing the thermal resistance between the emitters and the local environment, and thereby increasing lifetime, reliability, durability, and efficiency and reduce operating cost, pursuant to provision of the following:
1) A low solidity array which allows a portion of the solar load to be diverted to subsidiary surfaces and thereby make a smaller contribution to array heating. In addition, the open design allows airflow in and around the array and in very close thermal communication with the emitters.
2) Wind enhanced cooling. A porous array allows the passage of and the ability to transfer heat to the local air stream. Wind speed increases strongly with increasing height and high mounted signage and displays may benefit greatly from this cooling.
3) Thermally induced convection cooling caused by the wire array, the pixel packages, and by proper design of subsidiary surfaces behind the array (horizontal axis overlapping slats/louvers).
4) Solar assisted cooling may be promoted by proper design of subsidiary louvered absorber array behind the screen. Louver surfaces with a high absorptivity for sunlight and a low infrared emissivity may be used to further increase airflow.
5) The pixel package enables use of a rectangular copper substrate for LED mounting. This substrate acts as a thermal, electrical, and structural conduit and its cross section may be easily sized to provide sufficiently low thermal resistance. The pixel package is thermally coupled to the row and column wires to aid in the transport of heat to the local environment. In addition, the pixel package may be liquid filled to allow reduced LED operating temperature.
6) Active cooling may be used if necessary, but its need and its cost may be greatly reduced by the aforementioned features.
Provision is made for use of active and/or passively addressed pixels. Local (pixel based) electronics may be included in the pixel package and placed on the emitter substrate, behind the reflector, in the aluminum bushing and/or in the hemispherical cap. Local electronics may vary with application and include capacitors, resistors, inductors, diodes, transistors, standard integrated circuits such as 555 timers or application specific integrated circuits. Multiplexing may be used to reduce the cost of the electrical system, and the ability to multiplex is greatly increased by minimizing the pixel output radiation required by means discussed in the above optics section.
Provision is made for use of in-field replaceable pixels that may be made to be replaceable from either side of the screen.
Use of vertically oriented column/common wires and 45 degree oriented row/addressing wires to allows large scale seamless signage and displays with all pixels/electronics addressable/accessible from the top or the bottom of the screen.
Control electronics may be integrated into pixel packages; and/or control electronics may be concentrated in modules or zones at edge or edges of the arrays.
Provision is made for use of robust signage/displays created by arranging a parallel array of large diameter vertically oriented common/column wires in tension between horizontal upper and lower rigid members. The upper end of each vertical wire may be formed into a loop and affixed to and electrically isolated from the upper rigid horizontal member. The lower end of each vertical wire may be formed into a loop and elastically attached to and electrically isolated from the lower rigid member by a stainless steel extension spring. Both upper and lower mounts may serve to prevent rotation of the vertical wires around their own axes. A parallel array of 45 degree row wires may be connected in tension between the upper and lower rigid horizontal members by means analogous to those described for the vertical wire array. The 45 degree row wires may be constructed of a large diameter electrically insulated central wire helically wound with a 6 strand small diameter multifilar insulated wire array. The multifilar wire array includes paired red, green, and blue wires. The 45 degree wire array may be placed behind the vertical wire array and the pixel packages may be mounted in front of the vertical wires. The pixel packages may be mechanically connected to the vertical wires by plastic deformation of the pixel package aluminum bushing and/or the wire and/or by adhesives. The pixel common wire may be electrically connected to the large diameter vertical common wire through the aluminum bushing via wirebonding or pressure welding or directly to the larger diameter wire by soldering or pressure type connection. Red, green, and blue wires emanating from the pixel may be connected to the 45 degree row wires by soldering or by pressure type contacts.
The row and column wires may be constructed of aluminum to reduce cost and weight for a given strength, electrical and thermal conduction. In addition, electrically insulative coatings adhere better and have longer life on aluminum than copper.
Signage and displays of simple or complex face or form (circular or hyperbolic cylinders, cones and conoids, hyperbolic paraboloids) may be assembled on site or shop fabricated by simple techniques that lend themselves to manual or automated fabrication.
Other important advantages are listed as follows:
1. Organic Light Emitting Diodes: (OLEDS) may be used as light emitters alone or in conjunction with inorganic LEDs. OLEDs may be easier to apply to screen type substrates and may allow reduced product cost.
2. Multiplexing: The ability to tailor the angular extent of the radiation output and the increased contrast provided by the OnScreen design allows a greater degree of multiplexing and a concurrent reduction in system cost.
3. 45° Scanning: 45° scanning reduces line artifacts compared to vertical or horizontal scanning and thereby allows higher apparent resolution for a given number of pixels and/or a reduced number of pixels for a given apparent resolution.
4. In Field Pixel Replaceability: The ability to replace individual pixels in the field allows reduced maintenance cost.
5. Freedom of Form: Array construction allows a wide variety of signage/display forms. One example is a vertical axis cylindrical display viewed from the inside and/or the outside and with varying degree of array transparency determined by design.
6. Shop Or Site Fabrication: The light weight and flexible nature of the OnScreen array coupled with the mechanism of flexible local linkage allows for shop fabrication of large area arrays.
7. Pixel Level Voltage Reduction: Pixel “on-board” reduction allows higher array supply voltages and thereby lower current levels and reduced self-heating of array wiring and/or reduced wire cross-sectional area.